Environmental Engineering Reference
In-Depth Information
34
S) of various reduced sulfur compounds in the
Table 7.
The sulfur isotope composition (δ
upper layer of bottom sediments.
S
0
Station and
Layer, cm
H
2
S+
FeS
2
S
org
Reference
depth, m
FeHS
Shelf sediments, oxic zone
St. 2, 110 m
1-3
-20.5
-206
-19.9
-12.0
[94]
St. 3, 108 m
1-3
-21.1
-24.6
-20.0
+3.4
St. 708, 51 m
0-30
-
-22.2(3)
-28.6(5)
-13.9(3)
[73]
St. 752, 87 m
0-30
-
-23.3(3)
-28.5(5)
-17.0(3)
Average
-
-20.5
-22.7
-27.1
-12.7
Sediments of the anoxic zone
St. 4740, 2008 m
0-10
-24.0
-30.8
-33.2
-30.8
St. 4751, 2216 m
0-10
-21.1
-
-
-19.3
St. 4752, 2003 m
0-5
-29.4
-24.9
-27.4
-28.1
St. 4750, 2163 m
0-5
-32.1
-31.3
-30.6
-28.9
[94]
St. 4753, 1773 m
0-10
-27.4
-25.9
-33.7
-30.1
St. 4745, 1704 m
0-10
-31.2
-35.3
-33.7
-33.5
St. 4754, 1179 m
0-10
-30.5
-28.3
-26.3
-23.9
Average
-28.0
-29.7
-30.8
-27.8
the upper layers of the hydrogen sulfide zone with a source of suspended
organic matter from the zones of active photo- and chemosynthesis SRR
is much higher. The isotopic composition of sulfur of hydrogen sulfide
in these layers is heavier (δ
34
S = -35.2
÷
-39.0‰; Table 4).
3. In bottom sediments, minimum fractionation and the isotopically heavy
sulfides were found in coastal sediments with high SRR. In deep-sea
sediments of the hydrogen sulfide-containing zone with lower SRR, the
average isotope difference between sulfate and reduced sulfur is -56‰;
the average isotopic composition of the sum of the reduced sulfur com-
pounds is -31.8‰ (Table 5).
4. In subsurface sediments with active sulfate reduction, sulfate is enriched
with
34
S = 49.8 - 53.8‰ (Table 6), due to depletion of the
residual sulfate. The enrichment of all forms of reduced sulfur in
34
Sin
the subsurface happens due to their formation from isotopically heavy
residual sulfate (Table 6 and 7).
34
Suptoδ
5. Because of a considerable difference in the isotopic compositions of
hydrogen sulfide in the water column (δ
34
S
average
= -40.0‰; Table 2)
